Fitrah (Zakat al-Fitr) is a kaffarah for fasting person's unbefitting speech

The Messenger of Allah ﷺ prescribed Zakat al-Fitr as a purification ˹and a kaffarah (expiation)˺ of the fasting person for any empty and obscene talk and ˹for it to be˺ as food for the needy. If anyone pays it before the ˹Eid˺ prayer, it will be accepted as zakat. If anyone pays it after the prayer, that will be a sadaqah like other sadaqahs.  

فَرَضَ رَسُولُ اللَّهِ ﷺ زَكَاةَ الْفِطْرِ طُهْرَةً لِلصَّائِمِ مِنَ اللَّغْوِ وَالرَّفَثِ وَطُعْمَةً لِلْمَسَاكِينِ مَنْ أَدَّاهَا قَبْلَ الصَّلاَةِ فَهِيَ زَكَاةٌ مَقْبُولَةٌ وَمَنْ أَدَّاهَا بَعْدَ الصَّلاَةِ فَهِيَ صَدَقَةٌ مِنَ الصَّدَقَاتِ  

Ibn Abbas said: “The Messenger of Allah ﷺ enjoined Zakatul-Fitr as a purification for the fasting person from idle talk and obscenities, and to feed the poor. Whoever pays it before the (Eid) prayer, it is an accepted Zakah, and whoever pays it after the prayer, it is (ordinary) charity.”  

فَرَضَ رَسُولُ اللَّهِ ﷺ زَكَاةَ الْفِطْرِ طُهْرَةً لِلصَّائِمِ مِنَ اللَّغْوِ وَالرَّفَثِ وَطُعْمَةً لِلْمَسَاكِينِ فَمَنْ أَدَّاهَا قَبْلَ الصَّلاَةِ فَهِيَ زَكَاةٌ مَقْبُولَةٌ وَمَنْ أَدَّاهَا بَعْدَ الصَّلاَةِ فَهِيَ صَدَقَةٌ مِنَ الصَّدَقَاتِ  

The Messenger of Allah ﷺ prescribed the sadaqah (alms) relating to the breaking of the fast as a purification of the fasting from empty and obscene talk and as food for the poor. If anyone pays it before the prayer (of 'Id), it will be accepted as zakat. If anyone pays it after the prayer, that will be a sadaqah like other sadaqahs (alms). (Using translation from Abū Dāʾūd 1609)  

«فَرَضَ رَسُولُ اللَّهِ ﷺ زَكَاةَ الْفِطْرِ طُهْرَةً لِلصِّيَامِ مِنَ اللَّغْوِ وَالرَّفَثِ وَطُعْمَةً لِلْمَسَاكِينِ مَنْ أَدَّاهَا قَبْلَ الصَّلَاةِ فَهِيَ زَكَاةٌ مَقْبُولَةٌ وَمَنْ أَدَّاهَا بَعْدَ الصَّلَاةِ فَهِيَ صَدَقَةٌ مِنَ الصَّدَقَاتِ»  

"زكاة الفطر طهرةٌ للصائم من اللَّغو والرفث، وطُعْمةٌ للمساكين، مَنْ أدَّاها قَبْلَ الصلاةِ فهي زكاةٌ مقبولة، ومن أَدَّاها بعَد الصلاة فهي صَدَقةٌ من الصدقات".